//
// Copyright (c) 2004-2024 Jaroslaw Kowalski <jaak@jkowalski.net>, Kim Christensen, Julian Verdurmen
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// * Redistributions of source code must retain the above copyright notice,
//   this list of conditions and the following disclaimer.
//
// * Redistributions in binary form must reproduce the above copyright notice,
//   this list of conditions and the following disclaimer in the documentation
//   and/or other materials provided with the distribution.
//
// * Neither the name of Jaroslaw Kowalski nor the names of its
//   contributors may be used to endorse or promote products derived from this
//   software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
// THE POSSIBILITY OF SUCH DAMAGE.
//

namespace NLog.Internal
{
    using System;
    using System.Collections;
    using System.Collections.Generic;

    /// <summary>
    /// Ensures that IDictionary.GetEnumerator returns DictionaryEntry values
    /// </summary>
    internal
#if !NETFRAMEWORK
        readonly
#endif
        struct DictionaryEntryEnumerable : IEnumerable<DictionaryEntry>
    {
        private readonly IDictionary? _dictionary;

        public DictionaryEntryEnumerable(IDictionary? dictionary)
        {
            _dictionary = dictionary;
        }

        public DictionaryEntryEnumerator GetEnumerator()
        {
            return new DictionaryEntryEnumerator(_dictionary);
        }

        IEnumerator<DictionaryEntry> IEnumerable<DictionaryEntry>.GetEnumerator()
        {
            return GetEnumerator();
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }

        internal
#if !NETFRAMEWORK
            readonly
#endif
            struct DictionaryEntryEnumerator : IEnumerator<DictionaryEntry>
        {
            private readonly IDictionaryEnumerator _entryEnumerator;

            public DictionaryEntry Current => _entryEnumerator.Entry;

            public DictionaryEntryEnumerator(IDictionary? dictionary)
            {
                _entryEnumerator = dictionary?.Count > 0 ? dictionary.GetEnumerator() : EmptyDictionaryEnumerator.Default;
            }

            object IEnumerator.Current => Current;

            public void Dispose()
            {
                if (_entryEnumerator is IDisposable disposable)
                    disposable.Dispose();
            }

            public bool MoveNext()
            {
                return _entryEnumerator.MoveNext();
            }

            public void Reset()
            {
                _entryEnumerator.Reset();
            }
        }

        private sealed class EmptyDictionaryEnumerator : IDictionaryEnumerator
        {
            public static readonly IDictionaryEnumerator Default = new EmptyDictionaryEnumerator();
            public DictionaryEntry Entry => default;
            public object? Key => default;
            public object? Value => default;
            object? IEnumerator.Current => Entry;
            public bool MoveNext() => false;
            public void Reset()
            {
                // SONAR: Nothing to reset
            }
        }
    }
}
